|FISH LAKE VALLEY Level Line|
|Latitude: N 37°24'30.0"
Longitude: W 117°51'43.6"
Number of Bench marks: 10
Number of Surveys to 2000: 10
Date of Initial Survey: 30 September 1971
Date of Latest Survey: 28 March 2000
Trespass Permission: None needed, but the road is now posted as being in a wilderness area.
This line crosses the Furnace Creek fault on the west side of Fish Lake Valley, 4 miles SSW of the Esmeralda, Mono, and Inyo counties intersection (Fig. 1). The level line is located near an unnamed, posted access road 0.8 mile south of the windmill on Eureka Valley Road in Fish Lake Valley. It begins at monument 499, marked by a length of oil pump jack sucker rod pounded into the ground so that about 1/2 m of it protrudes above the ground surface. The array is near a small wash 10 m north of the access road, and it extends west across the alluvial fan on the west side the valley.
The line has been surveyed several times following earthquakes in the Bishop and Mammoth areas to determine if these earthquakes triggered vertical displacement on the Furnace Creek fault. The most recent surveys are plotted in Figure 2 and have such small variations in bench mark heights, that one may conclude that earthquakes to 2000 had no vertical effect on the fault, especially after the Chalfant Valley earthquake (M 6.2) of 21 July 1986, 50 km west-northwest of the array (Sylvester, 1989).
Fig. 1. Schematic map of Fish Lake Valley leveling array across the Fish Lake Valley fault in Fish Lake Valley.
|Fig. 2. Height changes and topographic profile of bench marks in Fish Lake Valley leveling array across the Fish Lake Valley fault. Uncertainty bars represent one standard deviation. One might postulate that five of the bench marks southwest of the fault have risen about 2 mm between Aug 1995 and Mar 2000, but the uncertainty allows the alternative interpretations the height change has been steady at less than 0.1 mm/yr, consistent with the geologic rates of uplift along the fault (Reheis and Sawyer, 1999), or that there has been no vertical displacement across the fault whatsoever in 29 years.|
Reheis, M. C., and T. L. Sawyer, 1999. Late Cenozoic history and slip
rates of the Fish Lake Valley, Emigrant Peak, and Deep Springs fault zones,
Nevada and California. Geological Society of America Bulletin 109, 280-299.
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